/*Binary Search-Search a sorted array by repeatedly dividing the search interval
 * in half. Begin with an interval covering the whole array. If the value of the
 * search key is less than the item in the middle of the interval, narrow the interval
 * to the lower half. Otherwise narrow it to the upper half. Repeatedly check until the
 * value is found or the interval is empty.
 */

function binarySearch(arr, i) {
    var mid = Math.floor(arr.length / 2);
    if (arr[mid] === i) {
        console.log("match", arr[mid], i);
        return arr[mid];
    } else if (arr[mid] < i && arr.length > 1) {
        binarySearch(arr.splice(mid, Number.MAX_VALUE), i);
    } else if (arr[mid] > i && arr.length > 1) {
        binarySearch(arr.splice(0, mid), i);
    } else {
        console.log("not found", i);
        return -1;
    }

}

var ar = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
binarySearch(ar, 3);
binarySearch(ar, 7);
binarySearch(ar, 13);